I encountered the same issue after installing a different keyboard than the Samsung default. When I restarted the phone (Samsung M33), the password required to be entered but there was no keyboard choice. I believe this is because I chose a different keyboard than the default Samsung keyboard earlier. I followed the procedures below to recover the phone without performing a factory reset.
I followed the instructions outlined here.
1) Start the phone in Safe Mode
2) The device reboots with limited functionality in sfae mode, only allowing system programs to run. This enabled me to change the default keyboards to Samsung and remove the third-party keyboard I was using.
3) One the 2nd step is done, restart the phone, and the Samsung keypad should be visible for entering passwords. Everything is normal.
How should the first step be carried out? That is, on the opening screen (Power On Mode), select Safe Mode. Take the actions outlined below.
* Simply press and hold the power and volume down buttons until the phone turns off.
* Press and hold the Volume down button when the Samsung logo shows while starting the phone.
* If everything is done correctly, Safe Mode will appear in the bottom left corner of the screen. Tap the Safe Mode.
* Steps 2 and 3 should be attempted from here.